VARIATION IN SUSPENDED SEDIMENT TRANSPORT IN A KARST SPRING AFTER STORMS

Suspended sediment levels in a karst spring vary in response to precipitation events. Understanding these sediment concentrations changes with respect to precipitation events leads to a clearer understanding of the variation in pathways through a karst network. We collected one sample daily for a thirty-one day period from Nolte Spring in southeastern Pennsylvania in Oct-Nov 2003. The samples were collected using an ISCO automatic sampler. The samples were filtered, and the total concentrations of sediments in each sample were calculated. These total concentrations were then compared with precipitation data collected about 10 km away at the Lancaster Airport.

Within the time frame of the experiment, total concentration of sediments varied from near 0 to 12.6 mg/L. Increased sediment concentration lagged two to three days behind significant (greater than 2cm) precipitation events. In comparing sediment concentrations following major precipitation events, we saw a flushing phenomenon. Following the first storm, a significant amount of sediment (11.6 mg/L) was present. Sediment concentrations following the second storm 13 days later rose no higher than 2 mg/L. Suspended sediment concentrations were high following the first storm because no significant precipitation had fallen in the 21 days prior to the storm. This allowed the sediment to accumulate in the system.